Mohsan Ali

1. Astrocyte-Derived Adenosine and A1 Receptor Activity Contribute to Sleep Loss-Induced Deficits in Hippocampal Synaptic Plasticity and Memory in Mice Mohsan Ali

2. Background • Sleep deprivation – Sleep loss - Cognitive deficits and function • SD increases extracellular adenosine levels in the forebrain and cortex. (Porkka-Heiskanen et al., 1997) • Astrocytes release ATP - ATP  Adenosine

3. Sleep • Classified into rapid eye movement (REM) and non-rapid eye movement (NREM) stages. • REM is characterized by high frequency, low amplitude. • NREM is characterized by low frequency, high amplitude

4. Sleep and Memory • Synaptic scaling hypothesis suggests that net nerve impulse increase during waking experience.(Liu et al., 2010) • Memory trace reactivation hypothesis suggests that memory during wakefulness replays itself during sleep. (Lee and Wilson, 2002)

6. Astrocytes • Modulate synaptic activity through ATP directly through P2 receptors. • Controlled through increased Ca2+ concentration • Specifically control slow oscillations during NREM

7. Slow Oscillation • Up state – is when action potential firing occurs - Generated by synaptic inputs • Down State – characterized by absence of synaptic inputs; membrane resting potential • Can be generated in cortical slices

9. Adenosine regulation • Derived from many sources in the nervous system • ATP is released in the extracellular and then hydrolyzed • Adenosine can be released through a direct pathway

10. Adenosine

11. dnSNARE mice • SNARE proteins mediate exocytosis of cellular transport vesicles. • dnSNARE mice can not carry out exocytosis • Astrocytic expression of dnSNARE significantly reduces extracellular adenosine.

13. A1R receptor • Adenosine binds to the A1R receptor, which causes inhibition of synaptic transmission. • Antagonists (CPT or DPCPX) bind to A1R receptor and enhance synaptic transmission. • At least four different adenosine receptors: A1R, A2AR, A2BR, and A3R

14. Slow Oscillation • During SD, sleep homeostat increases the drive to sleep - Sleep pressure • Sleep pressure is a measure by increased slow wave activity • dnSNARE mice reduce the slow oscillation power

16. Purpose • To demonstrate that astrocyte-derived adenosine and the adenosine receptor (A1R) play an important role in synaptic plasticity and memory deficits induced by SD. - Whether memory in the object recognition task is affected by SD.

17. Materials and Methods • dnSNARE mice were obtained by crossing two mouse lines. • Lights were maintained on a 12h light/dark cycle • WT and dnSNARE confirmed by PCR

19. Surgical Procedure • Brain cannula was placed at the left lateral ventricle. • Mini-osmotic pump was implanted between shoulder blades. • Coronal sections stained with cresyl violet.

21. Electrophysiology • Hippocampal slice preparation with ACSF • Electrode placed at the stratum radiatum to elicit action potentials • EPSPs recordings were made using ACSF-filled glass microelectrode

22. Spatial Object Recognition Task • Conducted in a gray rectangular box (40 X 30 X 30 cm) - polyvinyl chloride plastic • 6 minutes – removed • After 3 min, placed in box – two different objects for three cons. 6 minutes • Testing session

23. Data analysis • ANOVA was performed on all experiments > SPSS software - Linear regression slope • Comparison was made using t-test

24. Results • dnSNARE expression: - (-Dox) dnSNARE and EGFP are coexpressed - (+Dox) dnSNARE and EGFP are not expressed

30. Take Home Message… • Astrocyte modulate sleep through adenosine. • dnSNARE expressed in astrocyte reduces the power of slow oscillation. • SD causes increase in adenosine through astrocyte • SD impairs L-LTP in WT but not in dnSNARE. • Astrocytes modulate synaptic activity and memory through adenosine